The transcription factor NFkappaB plays a crucial role in modulating a large number of cellular processes including cell proliferation, cell differentiation and cell survival / cell death, and thus has been implicated in a variety of diseases including inflammation and autoimmune disease, Alzheimer's disease, and the escape of cancer cells for apoptosis. This collaborative application is focused on studying the role of NFkappaB in two different cell types, lymphocytes and neuronal cells. In both cell types, activation of NFkappaB is regulated by the IkappaB kinases (IKKs), which phosphorylate the inhibitory subunit IkappaB. Phosphorylated IkappaB is then conjugated to ubiquitin and degraded by the proteasome, thus resulting in release and nuclear translocation of active NFkappaB into the nucleus. In Aim 1, we will investigate the functions of IKKs in T cells, by determining (i) how the IKKs influence cytokine production by T cells; (ii) how the IKKs influence activation- induced death of T cells; and (iii) whether IKK activation in lymphocytes is selectively regulated by calcineurin. In Aim ii, we will evaluate whether IKKs regulate apoptosis in neuronal cells, by (i) investigating the activation of IKKs in response to selected apoptotic stimuli; (ii) asking whether IKK activation is required for apoptosis triggered by DNA damage (topisomerase II inhibition) and PI-3 kinase inhibition; (iii) asking whether pro- apoptotic molecules are regulated through IKK activity; and (iv) characterising IKK-dependent mRNAs linked to apoptosis. These questions will be addressed in selected lymphocyte and neuronal cell lines transfected with dominant negative and constitutively active IKKs, as well as in primary lymphocytes from transgenic mice in which the IKKs are expressed under tetracycline control in selected cell types.